Lens-to-camera mount adapters are used to attach a lens having a relatively large flange distance to a camera having a shorter flange distance. Adding a tilt function to such an adapter will allow a photographer to adjust the plane of focus to meet the Scheimpflug condition in order to increase depth of field, or alternately to intentionally violate the Scheimpflug condition in order to reduce the depth of field. Adding a shift function to a lens adapter will permit, among other things, the sensor plane to remain parallel to a wall or building while still taking in the full height of the subject. This will allow vertical lines in the object to be perfectly vertical in the image.
In order to take full advantage of tilting and shifting capability, the lens should have an image circle that is substantially larger in diameter than the actual image diagonal. So, for example, if a four-thirds format camera is used that has an image diagonal of 21.6 mm, it will be necessary to use a lens designed for a larger format, such as the DX format (28.8 mm image circle) or FX format (43.2 mm image circle).
It is also important that the flange distance (i.e. the distance from the lens mounting flange to the image surface) of the lens is substantially larger than the flange distance of the camera. The space between the two flanges will be filled with the lens-to-camera mount adapter, and the space needs to be adequately large to incorporate both tilting and shifting mechanisms.
Recently, cameras having a very short flange distance while also having a fairly large sensor (either four-thirds or DX) have become very popular. These are sometimes called “mirrorless” cameras because they use an electronic viewfinder rather than a single lens reflex viewing system. Elimination of the SLR type viewfinding system is what permits these cameras to have such a short flange distance. Examples of mirrorless cameras include the Sony NEX series of cameras, the Olympus series of Micro Four Thirds cameras, the Panasonic series of Micro Four Thirds cameras, and the Samsung NX series of cameras.
Many lens-to-camera mount adapters have been developed specifically for mirrorless cameras, ranging from simple adapters in which the camera and lens mounts are rigidly fixed with respect to each other, to adapters that permit either tilting or shifting. Currently there are no such adapters that permit both tilting and shifting.
One common problem with mirrorless cameras is that they are too small to provide a tripod mount that is sufficiently robust to support the camera when a large lens is attached. A lens-to-camera mount adapter is an ideal place to locate a robust tripod mount because the mounting location is closer to the center of gravity of the camera-plus-lens system. Also, the size and shape of a tripod mount located on a lens-to-camera mount adapter is not limited by the size and shape of the camera body. This means that the mount adapter can incorporate a quick-release tripod foot compatible with standard tripod heads such as Arca Swiss or Manfrotto. Currently, however, there are no such lens-to-camera mount adapters providing a robust tripod mount.
Many current lenses that would otherwise be ideal for mounting to mirrorless cameras via an adapter lack manual control of the iris diaphram. An excellent example are the “G” type lenses manufactured by Nikon. These lenses have no aperture ring. However, Nikon G lenses do have a mechanical aperture linkage in the mounting flange that can be controlled by a properly designed lens-to-camera mount adapter. Currently there are a variety of lens-to-camera mount adapters that provide manual control of lenses lacking manual iris control, but none of these adapters also provide both tilting and shifting functions.